Brake lining wear indicator

ABSTRACT

This invention relates to a device providing a warning signal to the vehicle operator when the brake lining has worn a predetermined amount.

[56] References Cited UNITED STATES PATENTS 4/1946 Edward K. Dombeck South Bend, Ind. [2]] Appl. No. 777,762

United States Patent [72] inventor 188/1UX l88/1X 188/78 188/1 188/1A 188/1X 116/67 188/196X.

3,020,873 2/1962 Brodkin......

3,138,224 6/1964 White.........

3,141,524 7/1964 Mishler 3,190,397 6/1965 Sudres........... 3,213,971 10/1965 Moyer et a1.... 3,368,519 2/1968 Ruda............. 3,388,774 6/1968 Burnett Primary Examiner-Louis J. Capozi [22] Filed Nov. 21, 1968 [45] Patented Jan. 19, 1971 [73] Assignee The Bendix Corporation a corporation of Delaware This invention relates to a device providing a warning signal to the vehicle operator when the brake lining has worn a predetermined amount.

Attorneys-Cecil F. Arens and Plante, Arens, Hartz and OBrien 1 16/ l 14, 1 88/1 601a 21/00 ABSTRACT: 1 16/ 1 l4, 205, 196, 78

mfi'i i'fi'gi 55711 1155" 4 Claims, 8 Drawing Figs.

[54] BRAKE LINING WEAR INDICATOR Int. [50] Field ofSearch..........

PATENIEUIJANIQISZI 3556046 SHEET 1. BF 2 q l l llllltlllll l' I N VEN TOR.

EDWARD K DOMBECK PATENTED JAM 9197! v SHEET 2 BF 2 lE.-.E

K mm m mm W v 0 W0 T 0 M K D m W E I" BRAKE LINING WEAR INDICATOR BACKGROUND OF THE INVENTION At the present time, the inspection of the condition of brake linings requires that the brake structure be disassembled in order to make the examination directly, and in the case of automobiles this requires the relatively laborious process of jacking up .the car and removing the wheels, and then reversing these stepsafterthe inspection is complete. While this procedure is merely inconvenient in the case where the brake linings are in a private 'or' pleasure automobile, in commercial vehicles, such astrucks, taxi cabs, buses, off-the-road vehicles andthe like, where there is a necessity fora continuous inspection or preventive maintenance program, this process is laborious, time consuming inefficient and costly.

Many devices have beendeveloped in the past to provide some type of signal toa vehicle operator to inform him that brake lining wear has progressed a predetermined amount. However, these devices have generally been sophisticated, bulky and very expensive. to manufacture. and install in vehicles. Moreover, the operational reliability of these devices has not been entirely satisfactory, ad thus, their anticipated widespread use hasnevermaterialized.

- SUMMARY OF 'I I-IEINVENTION It is an-object of thisinvention-to provide a brake lining wear indicator thatdoesnot require the brake structure to be disassembled todetermine ifthe linings are worn to the point that they need replacing.

It is an object of'thisinvention to provide aabrake lining wear indicator that'does' not interfere withnormal operation of the brake.

It is an object of thisinvention toprovide an immediate indication when the brake linings-reach a point of wear which requiresreplacement.

It is an object ofthis invention to provide a brake lining near indicator" then iscompact, easy to manufacture and install, and reasonably priced.

It is an object of this invention to'providea brake lining wear indicator thathas operational reliability. of a level heretofore unattainable. a

Itis an object of this inventionto provide brake liningwear indicator thatafter a predetermined amount'of lining wear provides a visual indication towarn that said liningis in need of replacement. A

It'is an object ofthis invention: to provide a'brake lining wearindicator' that aftera predetermined amount of lining wear provides an audibleindicationto warnthat said lining is in need of replacement:

Other-objects and features ofthe invention will be apparent from the followingdescription of the brake lining wear indicator takenin connection with. theaccompanyin'g drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. l is an elevationwiew. of abrake constructed in accordance with the preferred embodiment of this invention;

FIG. I ls an enlarged fragmentary sectional view taken substantially along linel lof FIG. land further including. a vehi- 'cle wheel;

FIG. 3 is an enlarged fragmentary sectional view of a modified form of theiinvention shown in FIG. 2;

FIG. 4 is an enlarged fragmentary): sectional view of a modified form of theinvention shown in FIG. 2';

FIG. 5:is an enlarged-fragmentary, sectional view of a modified form of the invention shown in FIG: 2

FIG. 6 is an elevation view of a brake constructed in accordance with the modifiedembodiment of this invention;

FIG. Tisa-sectionalview taken substantially alongJine 7-7 of FIG. 61andfurther including a vehicle wheel; and

FIG. 8 is anenlargedview-of the weariindicator rneans of p the modified embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, and especially FIGS. 1 and -2, there is illustrated a stationary support member 10 positioned along one side of a rotor 12, which is provided with annular opposed friction faces or surfaces 14 and 16. The rotor is connected to a wheel 11 and hub 13 by bolts 15. The stationary support member is attached to a fixed part of a vehicle, such as a spindle 18 having mounting bosses 19, by bolts 20 extending through the support member and bosses. The support member 10 has a pair or circumferentially spaced arms integral therewith for supporting a housing 26. The housing. 26 then straddles the rotor and is slidably mounted on the stationary support member 10- for movement in an axial direction toward and away from said rotor. This mounting method is morefullyexplained in US. Pat. Nos. 3,388,774 and 3,410,371, and have in common with this invention the same assignee. The housing 26 comprises a portion 30 extending radially inwardly adjacent one side of said rotor and another portion 32 extending radially inwardly along the side of and adjacent to the other side ofsaid rotor. The radial portions 30 and 32 are connected together by a bridge 34, thus providing a housing made from a single casting. An actuator 28 is located in the radial extending portion 30 and comprises a piston 36 slidably received in the bore 38. Appropriate seals are also provided to prevent escape of fluidfrom the chamber formed intermediate the piston 36 and the bore 38.

A friction element 50 is carried-by the radial portion 32 of the housing 26 and lies adjacent one face of the rotor'in contact therewith. The friction element 50, as shown herein, comprises a backing plate 56 and a friction lining 58.

The stationary support member 10,- which takes the braking torque, slidably supports a-friction element 60 between circumferentially spaced arms, not shown, for frictional engagement with a side of the rotor surface opposite to the siding gauge by the frictional element 50; The friction element 60' eomprisesa backing plate 61 and a friction lining 63. 4

The piston 36 of the actuator 28 is positioned adjacent the friction element 60 for moving the friction elementinto fric tional engagement'with the rotor 12, upon energization of the fluid motor or actuator 28. The housing 26 floatingly straddles the rotor 12 in such a manner that I10 36, and friction elements 50 and 60 are in substantial alignment. The actuator 28 is operatively connected to the friction element 60 via the piston 36, and to the friction element -50"through the housing 26 so thatthe application of hydraulic pressure causes the friction elements 50 and 60 to grip the rotor 12, thereby effecting a braking application. V

As may be seen then, friction linings 58 and 63 are in frictional engagement with surfaces 14 a 16' of the rotor 12 respectively during braking applications of the brake as-,

sembly. As best seen in FIG. 2, each of the friction linings 58 r and 63 has a wear indicating means 70 imbedded therein. The

wear indicator means 70 projects forward from the rear face of said lining a predetermined distance toward the front face for engagement with said rotor after said linings have worna predetermined amountto-tl'ie point where they need replacing. The wear indicator' means 70, shownin FIG. 2, is comprised of a semisolid a marking substance placed in the back of the lining segment before it is fastened to its respective steel backing plate. The semisolid marking substance is of such a texture as to not permanently scarthe rotor when it engages said rotor aftersaid predetermined amount of lining wear. The marking substance is designed such that when it contacts the disc or rotor it deposits a'noticeable streak on the disc, such thatupon' visual inspection one wouldnotice that the linings are worn to the point where they need replacing.

Referringnow briefly to FIG. 3, the wear indicator means I2 may be conical in shape. The: plugs after sufficient wearing of the linings 58 and 63 respectively. deposit first a narrow annular streak on the rotor 12, and as subsequent wear is experienced the streak becomes wider and wider until it approaches the diameter of said plug 71. With reference now to FIG. 4, said wear indicator means 70 may be comprised of a marking substance similar to the above-mentioned type, but substantially enclosed in a plastic plug 74 which, in turn, is press fit into openings or holes 72 of the backing plates of the friction members. FIG. 5 represents a modification of FIG. 4 wherein the wear indicator means 70 is comprised of a marking substance 73 suitably retained in a plug member 75 having a flange 76. The plug 74 is frictionally press fit into said opening 72 and flange 76 abuts the exterior surface of the backing plate. The flange 76 is an attempt to minimize any insertion error associated with the plug that could result from the embodiments shown in FIGS. 3 and 4. Specifically, the axial penetration toward the rotor by the plug 73 determines the point at which the marking substance begins to deposit a noticeable streak on the rotor 12. Thus, it is mandatory to control the predetermined distance between the marking end of the plug 73 and the rotor by controlling the axial penetration of said plug. The wear indicator means 70. as shown in FIGS. 3 and 4, have their predetermined axial distance between the marking ends of said means and the rotor established by controlling the exact overall length of said means and installing the back of said means flush with the rear surfaces of the respective backing plates.

DESCRIPTION OF THE MODIFIED EMBODIMENT The structure of the modified embodiment. as shown in FIGS. 6 and 7. that is identical to that shown and described in the preferred embodiment will be given the same identifying numbers.

As may be seen best in FIGS. 7 and 8, the friction member 50 is suitably installed to cooperate with a wear indicator means 80 comprised of a pin means 81. a retainer means 82. a weight 83. and a flexible cord 84. The pin means 81 is comprised of a shaft portion 85 and a flange portion 86. The pin means 81 is carried by the lining backing plate 56 in opening 87. The lining 58 has a relieved portion with an interior surface 88 against which the flange portion 86 abuts. The overall length of the pin means 81 and distance between the interior surface 88 and the interior surface of the backing plate 56 are predetermined such that upon installation of pin means 81, the end 89 of shaft portion 85 is flush with the back surface 90 of the backing plate 56. As may be seen best in H0. 6, the retainer means 82 is comprised of two or more resilient lever means 91 which protrude from back surface 90 of said friction member in a somewhat force opposing relationship to retain the weight 83 firmly against the end 89 of shaft portion 85. The lever means 91 may be rigidly secured to the backing plate 56 by spot welding, riveting, or other similar conventional techniques. Although said weight 83 is shown as a generally spherically shaped member it may be made in almost any physical configuration. The weight 83 extending from one end a stem portion 92 with a hole 93, in which is fastened the flexible cord 84, whose other end is firmly attached to one of the lever means 91.

After substantial wear has been experienced by the brake lining 58, the rotor 12 will frictionally wear away surface 88 of said lining 58 so as to frictionally engage flange portion 86 of the pin means 81. Subsequent braking applications will wear additional lining from the lining 58 and exert an axial pressure on said pin means 81 so that the end 89 of shaft portion will eventually disengage weight 83 from the retainer means 82. Upon disengagement of the weight 83 from the retainer means 82, the weight being attached by the flexible cord 84 to the retainer means 82 will engage or rattle against said wheel 11 as it turns, thus giving an audible indication to the operator of the vehicle that his brake shoe linings are worn to the point where they need replacement. As will be seen from the drawings the weight 83 will continue to engage the wheel ll as ion as the vehicle is in motion. It 18 also noted that during perio s when the vehicle is not being operated, it may be seen by visual inspection that the weight 83 has been disengaged from the retainer means 82 and thus the person inspecting said vehicle will be advised that the brake shoe linings are worn to the point where they need replacement.

Obviously, then, many modifications and variations of the present invention are possible in light of the above teachings; therefore it is intended to cover all changes and modifications of the embodiment set forth herein which do not constitute departures from the spirit and scope of the invention.

lclaim:

1. In a brake assembly:

a member to be braked;

a friction element for engagement with the member to be braked to effect a brake application;

said friction element including a lining and a backing plate;

said lining having an outer face for engagement with said member to be braked and an inner face secured to said backing plate; and

a plug of marking mate ial carried in said lining at a predetermined distance from said outer face, whereby upon wear of said lining past said predetermined distance a visually noticeable streak is deposited on said member to be braked.

2. The invention of claim 1, said backing plate having an opening extending therethrough:

a cartridge slidably received in said opening; and

said plug being mounted in said cartridge.

3. The invention of claim 2, said cartridge having a radially projecting flange for engagement with said backing plate to limit the penetration of the plug into said friction element thereby establishing said predetermined distance.

4. The invention of claim 1, the end of said plug facing toward said outer face being tapered whereby a relatively narrow streak is placed on the member to be braked upon wear of said lining a distance equal to said predetermined distance and an increasingly wider streak is placed on the member to be braked upon further wear of the lining. 

1. In a brake assembly: a member to be braked; a friction element for engagement with the member to be braked to effect a brake application; said friction element including a lining and a backing plate; said lining having an outer face for engagement with said member to be braked and an inner face secured to said backing plate; and a plug of marking material carried in said lining at a predetermined distance from said outer face, whereby upon wear of said lining past said predetermined distance a visually noticeable streak is deposited on said member to be braked.
 2. The invention of claim 1, said backing plate having an opening extending therethrough: a cartridge slidably received in said opening; and said plug being mounted in said cartridge.
 3. The invention of claim 2, said cartridge having a radially projecting flange for engagement with said backing plate to limit the penetration of the plug into said friction element thereby establishing said predetermined distance.
 4. The invention of claim 1, the end of said plug facing toward said outer face being tapered whereby a relatively narrow streak is placed on the member to be braked upon wear of said lining a distance equal to said predetermined distance and an increasingly wider streak is placed on the member to be braked upon further wear of the lining. 